The invention relates to a fluid system for the safe operation of a fluid-operable actuator, comprising a control device for the provision of control signals to a valve controller, a valve controller for the operation of fluid control valves, fluid control valves which are electrically connected to the valve controller and designed to influence fluid flows to at least one actuator, sensor means which are designed to detect an actuator state, in particular an actuator position, and to output sensor signals in accordance with the detected actuator state, and a monitoring device which is designed to process the sensor signals and to provide a monitoring signal to the valve controller.
From EP1061269 A2, there is known a fault detection device for detecting a malfunction of actuating drives; this comprises an actuator having a movable piston, a servovalve connected thereto by hydraulic lines, a fault detection device and an electronic control unit for outputting a set value to the control unit of the servovalve. In this publication, it is provided that the control position of the servovalve determines the direction and speed of the piston movement, wherein a first sensor is provided for detecting the control position of the servovalve and a second sensor is provided for detecting the position of the piston in the actuator housing, and wherein the control position and the piston position are transmitted to the control electronics. The fault detection device is connected to the sensors, the actual speed and direction of the actuator piston being determined from the signals of the second sensor, wherein a set value for the speed and direction of the actuator piston is determined from the set value for the control position of the servovalve for fault detection, and wherein these are related to the speed and direction of the actuator piston determined from the signals of the second sensor and a fault signal is output if any deviation exceeds a threshold value.
EP1266147 A1 discloses a fluid power system with a safety function for the safety-oriented control of at least one fluid power actuator, the system comprising at least one local control device for the control of the fluid power actuator via control means of the fluid power system, wherein at least one sensor is provided for transmitting at least one information on at least one operating state of the fluid power system to the local control device, and wherein the local control device is designed such that it can evaluate at least one information for determining at least one safety-critical state and that it takes a predetermined consequential action if the at least one safety-critical state is present.